SUPPLEMENTARY INFORMATION:

Throughout this document, “we,” “us,” and “our” refer to the EPA.

Table of Contents

I. Background for Proposed Action

A. PM_2.5 NAAQS

B. South Coast PM _2.5 Designations, Classifications, and SIP Revisions

II. Completeness Review of the 2024 South Coast PM_2.5 Plan

III. Clean Air Act Requirements for an Extension of a Serious Area Attainment Date

IV. Review of the South Coast PM_2.5 Extension Application

A. Demonstration That Attainment by Serious Area Attainment Date Is Impractical

B. Compliance With All Requirements and Commitments in the Implementation Plan

C. Demonstration That the Implementation Plan Includes the Most Stringent Measures

D. Demonstration of Attainment by the Most Expeditious Alternative Date Practicable

E. Application for an Attainment Date Extension

F. Other Factors That the EPA May Consider

V. Summary of Proposed Action and Request for Public Comment

VI. Statutory and Executive Order Reviews

I. Background for Proposed Action

A. PM_2.5 NAAQS

Under section 109 of the Clean Air Act (CAA or “Act”), the EPA has established NAAQS for certain pervasive air pollutants (referred to as “criteria pollutants”) and conducts periodic reviews of the NAAQS to determine whether they should be revised or whether new NAAQS should be established. On January 15, 2013, the EPA strengthened the primary annual NAAQS for PM_2.5 by lowering the level from 15.0 µg/m^[3] to 12.0 µg/m^[3] (“2012 annual PM_2.5 NAAQS”).^[1]

The EPA established the PM_2.5 NAAQS after considering substantial evidence from numerous health studies demonstrating that serious health effects are associated with exposures to PM_2.5 concentrations above these levels. Epidemiological studies have shown statistically significant correlations between elevated PM_2.5 levels and premature mortality. Other important health effects associated with PM_2.5 exposure include aggravation of respiratory and cardiovascular disease (as indicated by increased hospital admissions, emergency room visits, absences from school or work, and restricted activity dates), changes in lung function, and increased respiratory symptoms. Individuals particularly sensitive to PM_2.5 exposure include older adults, people with heart and lung disease, and children.^[2]

Sources can emit PM_2.5 directly into the atmosphere as a solid or liquid particle (primary PM_2.5 or direct PM_2.5), or PM_2.5 can form in the atmosphere (secondary PM_2.5) as a result of various chemical reactions from precursor emissions of nitrogen oxides (NO_X), sulfur oxides (SO_X ), volatile organic compounds (VOC), and ammonia.^[3]

B. South Coast PM2.5 Designations, Classifications, and SIP Revisions

The South Coast PM_2.5 nonattainment area is home to approximately 17 million people, has a diverse economic base, and contains one of the highest volume port areas in the world. For a precise description of the geographic boundaries of the South Coast PM_2.5 nonattainment area, see 40 CFR 81.305. The local air district with primary responsibility for developing a plan to attain the 2012 annual PM_2.5 NAAQS in the South Coast nonattainment area is the South Coast Air Quality Management District (SCAQMD or “District”). The District works cooperatively with the California Air Resources Board (CARB) in preparing these plans. Authority for regulating sources in the South Coast nonattainment area is split between the District, which has responsibility for regulating stationary and most area sources, and CARB, which has responsibility for regulating most mobile sources and some categories of consumer products.

Following promulgation of a new or revised NAAQS, the EPA is required under CAA section 107(d) to designate areas throughout the nation as attaining or not attaining the NAAQS. On January 15, 2015, the EPA designated and classified the South Coast area as “Moderate” nonattainment for the 2012 annual PM_2.5 NAAQS, effective April 15, 2015.^[4]

On April 27, 2017, CARB submitted the “Final 2016 Air Quality Management Plan (March 2017)” (“2016 PM_2.5 Plan”) to address the CAA requirements associated with the 2012 annual PM_2.5 NAAQS in the South Coast.^[5] The 2016 PM_2.5 Plan included a demonstration, to address the requirements of CAA section 189(a)(1)(B), that attainment of the 2012 annual PM_2.5 NAAQS by the December 31, 2021 Moderate area attainment date in the South Coast area was impracticable, despite the implementation of required control measures.^[6] The 2016 PM_2.5 Plan also included a request that the EPA ( printed page 35447) reclassify the nonattainment area from Moderate nonattainment to Serious nonattainment, and included a Serious area attainment demonstration, emissions inventories, attainment related plan elements, and control measure provisions.^[7] Effective December 9, 2020, the EPA approved or conditionally approved the portions of the 2016 PM_2.5 Plan that pertain to the Moderate area planning requirements for the 2012 annual PM_2.5 NAAQS in the South Coast nonattainment area and, pursuant to CAA section 188(b)(1), reclassified the area as a Serious nonattainment area.^[8]

Upon reclassification as a Serious PM_2.5 nonattainment area, the South Coast area became subject to a new statutory attainment date of as expeditiously as practicable but no later than the end of the tenth calendar year following designation ( i.e., December 31, 2025) and a requirement to submit a Serious area plan satisfying the requirements of CAA title I, part D, including the requirements of subpart 4, for the 2012 annual PM_2.5 NAAQS.^[9] As explained in the EPA's final reclassification action, the Serious area plan for the South Coast must include, among other things, provisions to assure that, under CAA section 189(b)(1)(B), the best available control measures (BACM) for the control of direct PM_2.5 and PM_2.5 precursors shall be implemented no later than four years after the area is reclassified and a demonstration (including air quality modeling) that the plan provides for attainment as expeditiously as practicable and no later than the applicable attainment date. The EPA also noted that California may choose to submit a request for an extension of the December 31, 2025, Serious area attainment date pursuant to CAA section 188(e).^[10]

Our final action on the 2016 PM_2.5 Plan's Moderate area requirements and reclassification of the nonattainment area to Serious noted that the submitted 2016 PM_2.5 Plan included Serious area planning elements for the 2012 annual PM_2.5 NAAQS and stated that we would evaluate and act on those elements through subsequent rulemakings as appropriate.^[11] On March 29, 2023, the CARB and the District notified the EPA of their determination that the portions of the 2016 PM_2.5 Plan pertaining to the Serious area planning requirements for the 2012 annual PM_2.5 NAAQS were no longer appropriate for inclusion in the SIP and requested that those portions of the submittal be considered withdrawn.^[12]

Following the State's withdrawal of the portions of the 2016 PM_2.5 Plan that pertained to the Serious area planning requirements for the 2012 annual PM_2.5 NAAQS, the EPA issued two findings that California had failed to submit SIP submissions to address the Serious area planning requirements for the 2012 annual PM_2.5 NAAQS. In the first finding, published in the Federal Register on May 26, 2023, the EPA found that California had failed to submit revisions to address the base year emissions inventory and BACM requirements, which the State was required to submit by June 9, 2022.^[13] In the second finding, published on January 30, 2024, the EPA found that California had failed to submit the Serious area plan requirements for a reasonable further progress (RFP) demonstration, quantitative milestones, an attainment demonstration, and contingency measures by December 31, 2023.^[14] These findings, which became effective on June 26, 2023, and February 29, 2024, respectively, triggered clocks under CAA section 179(a) for the application of emissions offset sanctions 18 months after the findings, and highway funding sanctions 6 months thereafter, unless the EPA affirmatively determined that the State made a complete SIP submission addressing the identified failure to submit deficiencies.^[15] The findings also triggered the obligation under CAA section 110(c) for the EPA to promulgate a Federal implementation plan no later than two years after the finding, unless the State has submitted, and the EPA has approved, the required SIP submission.^[16]

On August 6, 2024, CARB submitted the “South Coast Air Basin Attainment Plan for the 2012 Annual PM_2.5 Standard” (“2024 South Coast PM_2.5 Plan” or “Plan”), adopted by SCAQMD on June 7, 2024, and by CARB on June 27, 2024, to the EPA as a revision to the California SIP.^[17] The 2024 South Coast PM_2.5 Plan addresses the Serious area nonattainment plan requirements for the 2012 annual PM_2.5 NAAQS in the South Coast nonattainment area and includes a request under CAA section 188(e) for an extension of the Serious area attainment date for the area for these NAAQS from December 31, 2025, to December 31, 2030.

II. Completeness Review of the 2024 South Coast PM _2.5 Plan

CAA sections 110(a)(1) and (2) and 110(l) require each state to provide reasonable public notice and opportunity for public hearing prior to the adoption and submission of a SIP or SIP revision to the EPA. To meet this requirement, every SIP submission should include evidence that the state provided adequate public notice and an opportunity for a public hearing consistent with the EPA's implementing regulations in 40 CFR 51.102.

CAA section 110(k)(1)(B) requires the EPA to determine whether a SIP submission is complete within 60 days of receipt. This section also provides that any plan that the EPA has not affirmatively determined to be complete or incomplete will become complete by operation of law six months after the date of submission. The EPA's SIP completeness criteria are found in 40 CFR part 51, appendix V.

On December 17, 2024, the EPA issued a letter finding that the emissions inventory and BACM elements of the 2024 South Coast PM_2.5 Plan conform to the EPA's completeness criteria in 40 CFR part 51, appendix V.^[18] On June 9, 2025, the EPA issued a second letter finding that the RFP demonstration, quantitative milestones, attainment demonstration, and contingency measures elements of the Plan also conform to the completeness criteria in 40 CFR part 51, appendix V.^[19] These completeness findings corrected the deficiencies identified in the EPA's previous findings of failure to submit, and terminated the sanctions clocks started by the findings.

( printed page 35448)

III. Clean Air Act Requirements for an Extension of a Serious Area Attainment Date

Under section 188(e) of the Act, a state may apply to the EPA for a single extension of the Serious area attainment date by up to five years, which the EPA may grant if the state satisfies certain conditions. Before the EPA may extend the attainment date for a Serious area under CAA section 188(e), the state must:

(1) Demonstrate that attainment by the Serious area attainment date is impracticable;

(2) Demonstrate that it has complied with all requirements and commitments pertaining to the area in the implementation plan;

(3) Demonstrate to the satisfaction of the Administrator that the plan for the area includes the “most stringent measures” (MSM) that are included in the implementation plan of any State or are achieved in practice in any State, and can feasibly be implemented in the area;

(4) Submit a modeled attainment demonstration showing attainment of the NAAQS in the area by the most expeditious alternative date practicable; and

(5) Apply for an extension of the attainment date beyond the Serious area attainment date.^[20]

A state must seek an extension of the Serious area attainment date at the same time it submits the Serious area attainment plan if the state cannot demonstrate attainment by the otherwise applicable statutory attainment date.^[21]

The EPA established regulatory requirements and provided further interpretive guidance on the statutory SIP requirements that apply to areas designated nonattainment for the PM_2.5 standards in an August 24, 2016 final rule titled “Fine Particulate Matter National Ambient Air Quality Standards: State Implementation Plan Requirements” (“PM_2.5 SIP Requirements Rule”).^[22] Under the EPA's regulations at 40 CFR 51.1005(b)(2), a state seeking an extension of the Serious area attainment date under CAA section 188(e) must also submit a Serious area attainment plan that meets the following requirements:

(1) Base year and attainment projected emissions inventory requirements in 40 CFR 51.1008(b);

(2) The MSM requirement in 40 CFR 51.1005(b)(1)(iii) and 51.1010(b), and best available control measures not previously submitted;

(3) Attainment demonstration and modeling requirements in 40 CFR 51.1005(b)(1)(i) and 51.1011;

(4) RFP requirements in 40 CFR 51.1012;

(5) Quantitative milestone requirements in 40 CFR 51.1013;

(6) Contingency measure requirements in 40 CFR 51.1014; and

(7) Nonattainment new source review plan requirements pursuant to 40 CFR 51.165.^[23]

In addition to establishing specific preconditions for an extension of the Serious area attainment date, CAA section 188(e) provides that the EPA may consider a number of factors in determining whether to grant an extension and the appropriate length of time for any such extension. These factors are: (1) the nature and extent of nonattainment in the area, (2) the types and numbers of sources or other emitting activities in the area (including the influence of uncontrollable natural sources and trans-boundary emissions from foreign countries), (3) the population exposed to concentrations in excess of the standard in the area, (4) the presence and concentrations of potentially toxic substances in the mix of particulate emissions in the area, and (5) the technological and economic feasibility of various control measures.^[24] Notably, neither the statutory requirements nor the discretionary factors identified in CAA section 188(e) include the specific ambient air quality conditions in CAA section 188(d)(2), which must be met for an area to qualify for an extension of a Moderate area attainment date.

The EPA is evaluating the State's request for an extension of the Serious area attainment date in accordance with these statutory criteria and regulatory requirements, as further described below.

1. Demonstrate That Attainment by the Serious Area Attainment Date Is Impracticable

Section 188(e) of the Act authorizes the EPA to grant a state request for an extension of the Serious area attainment date if, among other things, attainment by the date established under CAA section 188(c) would be impracticable. In order to demonstrate impracticability, EPA guidance has stated that the plan must show that the implementation of best available control measures (BACM) and best available control technology (BACT) (and additional feasible measures) on relevant source categories will not bring the area into attainment by the statutory Serious area attainment date.^[25] For the South Coast, the Serious area attainment date for the 2012 annual PM_2.5 NAAQS under CAA section 188(c)(2) is December 31, 2025.^[26]

The EPA has defined BACM in the PM_2.5 SIP Requirements Rule to mean “any technologically and economically feasible control measure that can be implemented in whole or in part within 4 years after the date of reclassification of a Moderate PM_2.5 nonattainment area to Serious and that generally can achieve greater permanent and enforceable emissions reductions in direct PM_2.5 emissions and/or emissions of PM_2.5 plan precursors from sources in the area than can be achieved through the implementation of RACM on the same source(s). BACM includes BACT.” ^[27]

Consistent with longstanding EPA guidance,^[28] the preamble to the PM_2.5 SIP Requirements Rule discusses the following steps for determining BACM and BACT:

(1) Develop a comprehensive emission inventory of the sources of PM_2.5 and PM_2.5 precursors;

(2) Identify potential control measures;

(3) Determine whether an available control measure or technology is technologically feasible;

(4) Determine whether an available control measure or technology is economically feasible; and

(5) Determine the earliest date by which a control measure or technology can be implemented in whole or in part.^[29]

The EPA allows consideration of factors such as physical plant layout, energy requirements, needed infrastructure, and workforce type and ( printed page 35449) habits when considering technological feasibility. For purposes of evaluating economic feasibility, the EPA allows consideration of factors such as the capital costs, operating and maintenance costs, and cost effectiveness ( i.e., cost per ton of pollutant reduced by a measure or technology) associated with the measure or control.^[30]

2. Comply With All Requirements and Commitments in the Applicable Implementation Plan

A second precondition for an extension of the Serious area attainment date under CAA section 188(e) is a showing that the state has complied with all requirements and commitments pertaining to that area in the implementation plan. We interpret this criterion to mean that the state has implemented the control measures and commitments in the SIP revisions it has submitted to address the applicable requirements in CAA sections 172 and 189 for that particular PM_2.5 nonattainment area; in this case, the South Coast nonattainment area for the 2012 annual PM_2.5 NAAQS.^[31] For a Serious area attainment date extension request submitted simultaneously with the initial Serious area attainment plan for the area, the EPA interprets CAA section 188(e) not to require the area to have a fully approved Moderate area attainment plan, and to allow for extension of the attainment date if the area has complied with all Moderate area requirements and commitments pertaining to that area in the State's submitted Moderate area implementation plan.^[32] This interpretation is based on the plain language of CAA section 188(e), which requires the state to comply with all requirements and commitments pertaining to the area in the implementation plan.^[33]

3. Demonstrate the Inclusion of the Most Stringent Measures

A third precondition for an extension of the Serious area attainment under CAA section 188(e) is for the state to demonstrate to the satisfaction of the Administrator that the plan for the area includes the MSM that are included in the implementation plan of any State, or are achieved in practice in any State, and can feasibly be implemented in the area. The EPA has defined the term MSM as “any permanent and enforceable control measure that achieves the most stringent emissions reductions in direct PM_2.5 emissions and/or emissions of PM_2.5 plan precursors from among those control measures which are either included in the SIP for any other NAAQS, or have been achieved in practice in any state, and that can feasibly be implemented in the relevant PM_2.5 NAAQS nonattainment area.” ^[34] The EPA has interpreted the Act to require implementation of MSM as expeditiously as practicable and no later than one year before the extended Serious area attainment date identified by the state in its extension request.^[35]

An MSM demonstration must satisfy the requirements of the PM_2.5 SIP Requirements Rule as described in the preamble to the rule, as follows: ^[36]

(1) Update the emission inventory to identify all sources of direct PM_2.5 and all PM_2.5 precursor emissions in the nonattainment area;

(2) Identify all potential MSM to reduce emissions from sources of direct PM_2.5 and PM_2.5 plan precursors that are approved into any state implementation plan or used in practice in any state;

(3) Compare the potential MSM for each relevant source category to the measures, if any, already adopted for that source category in the nonattainment area to determine whether such potential MSM would further reduce emissions and, where the state chooses to reject a measure from further consideration, demonstrate that it is not technologically or economically feasible to implement the measure in whole or in part within five years after the applicable attainment date for the area; and

(4) Adopt and implement all potential MSM identified through this process that collectively will achieve attainment as expeditiously as practicable and no later than five years after the applicable attainment date, except those measures for which the state has provided reasoned justification for rejection, based on technological or economic feasibility.

Notably, the “to the satisfaction of the Administrator” qualifier on the MSM requirement is an explicit grant by Congress to the EPA of discretion to determine whether a plan includes MSM.

4. Submit a Demonstration of Attainment by the Most Expeditious Alternative Date Practicable

Section 189(b)(1)(A) of the Act requires that the State submit a demonstration of attainment, including air quality modeling, by the most expeditious date practicable after the statutory Serious area attainment date.^[37] CAA section 188(e) states that the threshold requirement is submission of such a demonstration.^[38] Accordingly, the EPA must evaluate whether the submission containing the extension request also includes such a demonstration.

5. Apply for an Attainment Date Extension

Finally, the state must apply in writing to the EPA for an extension of a Serious area attainment date, and this request must accompany the submission of the modeled attainment demonstration showing attainment by the most expeditious alternative date practicable. Additionally, the state must provide the public reasonable notice and opportunity for a public hearing on the attainment date extension request before submitting it to the EPA in accordance with the requirements for SIP revisions in CAA section 110.

IV. Review of the South Coast PM_2.5 Extension Application

In this section of the preamble, we present our evaluation of the State's request to extend the Serious area ( printed page 35450) attainment date from December 31, 2025, to December 31, 2030, under CAA section 188(e).

A. Demonstration That Attainment by Serious Area Attainment Date Is Impracticable

The 2024 South Coast PM_2.5 Plan includes a demonstration, based on air quality modeling, that even with the implementation of BACM and BACT for all appropriate sources, attainment by December 31, 2025, is not practicable. The impracticability demonstration is included in Chapter 6 (“Federal Clean Air Act Requirements”) of the 2024 South Coast PM_2.5 Plan, which references the State's modeling results in Chapter 5 (“Future Air Quality”) of the Plan. The BACM/BACT demonstration is included in Appendix III (“Stationary and Mobile Source BACM/MSM”). Because of the substantial overlap in the source categories and controls evaluated for BACM and those evaluated for MSM, the BACM demonstration is discussed alongside our evaluation of the Plan's MSM demonstration in section IV.C of this document.

Table 5-4 of the Plan presents base year and modeled 2025 annual PM_2.5 design values at 17 PM_2.5 monitoring sites in the South Coast nonattainment area. The demonstration is summarized in table 1 of this document.

The State projected that the annual design value in the South Coast nonattainment area in 2025 would be 13.09 µg/m³ , which is substantially above the 12.0 µg/m³ level of the 2012 annual PM_2.5 NAAQS. Thus, we find it reasonable to conclude based on the State's evaluation that attainment by the end of 2025 was impracticable.

In addition to the information in the South Coast PM_2.5 Plan, we have reviewed recent PM_2.5 monitoring data from the South Coast Air Basin. These data show that annual average PM_2.5 levels in the South Coast remained above the 12.0 µg/m^[3] level of the 2012 annual PM_2.5 NAAQS in 2024 at eight monitoring sites in the South Coast nonattainment area.^[39] Furthermore, based on monitored ambient PM_2.5 air quality data from 2023 and 2024, we calculated the maximum 2025 annual average concentration that would result in an attaining 2025 design value ^[40] at the historical design value site in the nonattainment area,^[41] and compared this concentration to the lowest recorded annual average since 2012. This comparison is shown in table 2 below.

( printed page 35451)

The EPA's monitoring analysis determined that the maximum 2025 annual average concentration that would result in an attaining 2025 design value at the historical design value site in the nonattainment area is 9.5 µg/m³ , approximately 33 percent below the monitored annual average PM_2.5 concentration from the previous year, and approximately 22 percent lower than the lowest annual average PM_2.5 concentration recorded at this site since it was established in 2015. Although the certified data for 2025 are not yet available, the available data indicate that it is infeasible for the area to attain by the December 31, 2025 attainment date.

Thus, our review of the State's impracticability demonstration and of the available ambient air quality data indicate that the South Coast area could not practicably have attained the 2012 annual PM_2.5 NAAQS by the applicable attainment date of December 31, 2025.

B. Compliance With All Requirements and Commitments in the Implementation Plan

We interpret this criterion to mean that the State has implemented the control measures and commitments in the plan revisions it has submitted to address the applicable requirements in CAA sections 172 and 189 for the relevant PM_2.5 NAAQS for the nonattainment area.^[42] For the South Coast for the 2012 annual PM_2.5 NAAQS, the State has submitted, and the EPA has approved into the California SIP, the control measure requirements and commitments in the 2016 PM_2.5 Plan that pertained to the Moderate area planning requirements for the 2012 annual PM_2.5 NAAQS. In the remainder of this section, we describe the State's and District's implementation of those control measures and commitments.

As discussed in section I of this document, CARB submitted the 2016 PM_2.5 Plan to the EPA on April 27, 2017.^[43] On November 9, 2020, the EPA approved all but the contingency measure element of the submitted SIP revision as meeting all applicable Moderate area requirements for the 2012 annual PM_2.5 NAAQS, and conditionally approved the contingency measure element as meeting the Moderate area contingency measure requirement.^[44] The State subsequently withdrew those portions of the 2016 PM_2.5 Plan pertaining to the Serious area planning requirements for the 2012 annual PM_2.5 NAAQS, including those commitments intended to meet the Serious area plan requirements.

A majority of the emission reductions needed to demonstrate RFP in the South Coast nonattainment area in the 2016 PM_2.5 Plan came from rules and regulations that were adopted prior to the submittal of the Plan in April 2017. However, the State determined as part of its RFP analysis for the 2016 PM_2.5 Plan that an additional 7 tons per day (tpd) of NO_X emission reductions from new or revised control strategy measures was necessary to show linear progress towards attainment by the Serious area attainment date and thereby meet the 2022 RFP milestone.^[45] As part of the EPA's November 9, 2020 final action on the 2016 PM_2.5 Plan, the EPA approved, among other things, the District's commitment to achieve 7 tpd of direct PM_2.5 emission reductions from these or substitute measures by the 2022 RFP milestone year.^[46]

Additionally, for purposes of meeting the Moderate area RFP contingency measure requirement for the 2012 annual PM_2.5 NAAQS,^[47] the District and CARB committed to develop, adopt, and submit a revised District rule, SCAQMD Rule 445, “Wood-Burning Devices” (“Rule 445”). The EPA conditionally approved the contingency measure element of the 2016 PM_2.5 Plan, including the State's commitment to revise Rule 445, as meeting the Moderate area planning requirements for contingency measures for the 2012 annual PM_2.5 NAAQS.

The State discusses compliance with the applicable 2016 PM_2.5 Plan Moderate area planning requirements and commitments for the 2012 annual PM_2.5 NAAQS in Chapter 6 (“Federal Clean Air Act Requirements”) of the 2024 South Coast PM_2.5 Plan.

Regarding the 7 tpd of NO_X reductions needed to demonstrate RFP in the 2022 milestone year, the District states that it has achieved reductions in excess of those projected in the 2016 PM_2.5 Plan.^[48] Specifically, the District states that a large portion of the reductions were achieved through mobile source incentive measures under District control measure MOB-14 (“Emission Reductions from Incentive Programs”).^[49] The incentive programs include the Carl Moyer Program, Proposition 1B—Air Quality Improvement Fund, the Lower-Emission School Bus Program, and the Community Air Protection Program. Emission reductions from these programs are summarized in Table 6-4 of the 2024 South Coast PM_2.5 Plan and amount to 13.99 tpd of NO_X, with reductions from the Carl Moyer and Prop 1B programs alone exceeding the 7 tpd needed to demonstrate RFP, totaling 11.39 tpd of NO_X reductions.^[50] In addition to the reductions from incentive programs, the District identified further surplus NO_X reductions in 2022 from Rule 445; Rule 1109.1, “NO_X Emissions From Petroleum Refineries;” Rule 1179.1, “Emission Reductions From Combustion Equipment at Publicly Owned Treatment Works Facilities;” and from the general conformity set-aside account.^[51]

Regarding CARB's and the District's commitment to develop, adopt, and submit a revised version of SCAQMD Rule 445, the District amended Rule 445 for purposes of meeting the PM_2.5 contingency measure commitment on June 5, 2020. On October 27, 2020, the District made additional revisions to the rule while retaining the June 5, 2020 PM_2.5 contingency measure revisions ( printed page 35452) unchanged.^[52] The June 5, 2020 amendments to Rule 445 included the addition of new lower mandatory wood-burning curtailment provisions in section (f) (“PM_2.5 Contingency Measures”) to be implemented as contingency measures upon a determination by the EPA that any of the four “findings of failure” listed under 40 CFR 51.1014(a) has occurred.^[53] The EPA approved SCAQMD Rule 445, as amended on October 27, 2020, except paragraph (g) (“Ozone Contingency Measures”) and paragraph (k) (“Penalties”), into the California SIP on March 8, 2022.^[54] We also determined that the submitted rule fulfilled CARB's and the District's commitment to adopt and submit a specific enforceable contingency measure to address CAA requirements for the 2012 annual PM_2.5 NAAQS in the South Coast Air Basin and, on that basis, converted our November 9, 2020 conditional approval to a full approval.^[55]

Based on our review, we are proposing to find that the State has complied with all the Moderate area requirements and commitments in the 2016 PM_2.5 Plan, which is the applicable implementation plan for the purposes of 51.1005(b)(1)(ii) for the 2012 annual PM_2.5 NAAQS.

C. Demonstration That the Implementation Plan Includes the Most Stringent Measures

Before the EPA may extend the attainment date for a Serious nonattainment area under CAA section 188(e), the state must, among other things, demonstrate to the satisfaction of the Administrator that the plan for the area includes the most stringent measures (MSM) that are included in the implementation plan of any state or are achieved in practice in any state, and can feasibly be implemented in the area. The state must implement MSM as expeditiously as practicable and no later than the beginning of the year containing the attainment date identified by the state in its extension request, i.e., in this case, by January 1, 2030.^[56] We interpret this criterion to mean that the State must demonstrate to the EPA's satisfaction that its Serious area plan includes the most stringent measures that are included in the implementation plan of any state, or achieved in practice in any state, and can feasibly be implemented in the area. The requirements that a state's MSM evaluation must satisfy are described in the PM_2.5 SIP Requirements Rule and are summarized in section III of this document.

The 2024 South Coast PM_2.5 Plan discusses the Plan's control strategy, including compliance with the BACM and MSM requirements, in Chapter 4 (“Control Strategy”), and contains BACM and MSM evaluations in Appendix III (“Stationary and Mobile Source BACM/MSM”). The evaluations consist of analyses by CARB and the District of source categories under their respective jurisdictions. Emissions inventories identifying sources of emissions of direct PM_2.5 and PM_2.5 precursors ^[57] in the South Coast Air Basin are described and included in Chapter 3 (“Emissions Inventory”) and Appendix I (“Base and Future Year Emission Inventory”) of the Plan.

CARB's BACM/MSM analysis for sources under the State's jurisdiction is contained in Attachment B (“Most Stringent Measures Analysis of CARB's Control Programs”) to Appendix III of the 2024 South Coast PM_2.5 Plan. CARB's four-step process to assess the State's control program consists of: (1) identifying sources of direct PM_2.5 emissions and precursor emissions; (2) identifying potential control measures for the sources identified in Step 1; (3) assessing the stringency and feasibility of the control measures identified in Step 2; and (4) adopting and implementing the feasible control measures identified in Step 3. CARB's demonstration includes descriptions of CARB's key mobile source programs and regulations, and a comprehensive evaluation of on-road and non-road mobile source regulatory actions taken by CARB and other states. Based on its review, CARB determined that its current control program for sources under its jurisdiction satisfies the BACM and MSM requirements.^[58]

The District followed a similar process to identify candidate BACM/MSM measures that are technologically and economically feasible for stationary and area sources under its jurisdiction. As a first step, SCAQMD examined the emissions inventory to identify key sources of emissions of direct PM_2.5 . Based on these inventories, the District identified residential wood combustion, paved road dust, commercial cooking, and farming operations—livestock waste as key emission sources of direct PM_2.5 in the South Coast nonattainment area.^[59] Next, the District broadened its analysis to assess potential controls across all applicable source categories under its jurisdiction. The District reviewed existing control measures implemented in the South Coast Air Basin and compared those controls to Federal and State regulations and guidance, as well as analogous rules implemented by other air agencies to assess the stringency of existing controls and identify potential opportunities to achieve further reductions. More specifically, the District (1) conducted an in-depth analysis of control measures in the SIPs for other 2012 annual PM_2.5 NAAQS nonattainment areas ( i.e., San Joaquin Valley, CA; Plumas County, CA; Imperial County, CA; and Allegheny County, PA) to evaluate whether control technologies deemed available and cost-effective in those areas would be feasible in the South Coast Air Basin; (2) reviewed EPA technical support documents for previously adopted/amended rules submitted for approval into the California SIP; (3) reevaluated control measures that the District had found to be technologically or economically infeasible as part of the controls evaluations in the 2016 and 2022 air quality management plans (AQMPs); (4) reviewed the EPA's Menu of Control Measures; ^[60] and (5) reviewed ( printed page 35453) the EPA's applicable guidance documents.

Based on its analysis, the District identified 15 control measures for evaluation as potential BACM/MSM.^[61] The District's analyses include descriptions of the measures, estimates of potential emissions reductions and assessments of technological and economic feasibility. As a result of these analyses, SCAQMD concluded that four of the measures, identified in Table 4-4 of the Plan, are feasible and should be adopted and implemented as MSM,^[62] and included commitments to adopt each of these four measures as part of the control strategy of the Plan.^[63] SCAQMD determined that the remaining measures were not feasible for implementation in the South Coast Air Basin.

Based upon our review, the EPA has determined that the 2024 South Coast PM_2.5 Plan contains the required elements of BACM and MSM evaluations as described in the PM_2.5 SIP Requirements Rule. The emissions inventory identifies all sources of emissions of direct PM_2.5 and applicable PM_2.5 precursors. For the source categories identified in the emissions inventory for the nonattainment area, CARB and the District followed EPA guidance to identify potential measures from other areas' control requirements for similar sources, the EPA's technical support documents from rulemakings on SCAQMD control measure SIP submittals, potential control measures identified in previous SCAQMD plan submittals, the EPA's menu of control measures, and EPA guidance documents.

Our review indicates that CARB and the District conducted thorough analyses of emissions sources in the nonattainment area and potential control measures for those sources. The 2024 South Coast PM_2.5 Plan includes commitments and an expeditious schedule for adopting the four measures identified by the District as MSM, and provides a reasoned justification for the rejection of all other potential MSM based on technological or economic feasibility, consistent with the requirements established in the PM_2.5 SIP Requirements Rule. The District has since adopted the four measures and submitted them to the EPA for inclusion in the California SIP.^[64] The EPA is not aware of more stringent and feasible measures implemented in other areas of the country beyond those identified in the 2024 South Coast PM_2.5 Plan. Thus, our review indicates that the 2024 South Coast PM_2.5 Plan includes the requisite BACM demonstration and includes the MSM that are included in the implementation plan of any state, or are achieved in practice in any state, and can feasibly be implemented in the area.

D. Demonstration of Attainment by the Most Expeditious Alternative Date Practicable

Section 188(e) of the Act states that at the time of its application for an extension of an attainment deadline, the state must submit a demonstration of attainment by the most expeditious alternative date practicable, and that the EPA may not approve the extension until such a demonstration has been submitted. Section 189(b)(1)(A)(ii) of the CAA also provides that a state seeking an extension of the attainment date under CAA section 188(e) must submit a demonstration that the plan provides for attainment by the most expeditious alternative date practicable.

For the purpose of the CAA section 188(e) requirement that the District submit a demonstration that the plan provides for attainment by the most expeditious alternative date practicable, the EPA's review of the submission indicates that the submission contains the requisite demonstration. Chapter 5 (“Future Air Quality”) of the 2024 South Coast PM_2.5 Plan contains the State's demonstration of attainment by 2030, and an analysis concluding that attainment by 2029 would not be possible.^[65] While the EPA will evaluate this analysis in a future rulemaking action, for the purpose of the CAA section 188(e) extension prerequisite that a complete submission from the state must contain the requisite demonstration under CAA section 189(b)(1)(A)(ii), our review of the 2024 South Coast PM_2.5 Plan indicates that the State has made such a submission.

E. Application for an Attainment Date Extension

As discussed in section I.B of this document, the Serious area attainment date for the South Coast for the 2012 annual PM_2.5 NAAQS under CAA section 188(c)(2) is December 31, 2025. The remaining criterion for an extension of the attainment date beyond this statutory attainment date is that the State must apply for such extension. In the 2024 South Coast PM_2.5 Plan, CARB and SCAQMD submitted a complete application for an extension of the Serious area attainment date for the South Coast to December 31, 2030, for the 2012 annual PM_2.5 NAAQS.^[66] In accordance with the requirements of the PM_2.5 SIP Requirements Rule in 40 CFR 51.1005(b)(1), the State's submission includes demonstrations that attainment by the Serious area attainment date is impracticable, that the State has complied with all requirements and commitments in the applicable SIP, and that the plan includes MSM. Additionally, in accordance with 40 CFR 51.1005(b)(2), the 2024 South Coast PM_2.5 Plan contains all of the required components of a Serious area plan accompanying a request for extension of the attainment date under CAA section 188(e), as follows: (1) base year and attainment projected emissions inventories, (2) provisions to implement MSM and BACM, (3) a modeled attainment demonstration, (4) reasonable further progress provisions, (5) quantitative milestone provisions, (6) contingency measure provisions, and (7) nonattainment new source review plan provisions.^[67] As discussed in section II ( printed page 35454) of this document, the EPA previously found that the State provided the public reasonable notice and an opportunity for a public hearing on the 2024 South Coast PM_2.5 Plan, including the attainment date extension request, before submitting it to the EPA, in accordance with the requirements for SIP revisions in CAA section 110.

F. Other Factors That the EPA May Consider

Finally, as noted section III of this document, CAA section 188(e) lists five additional factors that the EPA may consider in deciding whether to grant an attainment date extension and the length for such extension. These factors include: (1) the nature and extent of the nonattainment problem; (2) the types and numbers of sources or other emitting activities in the area (including the influence of uncontrollable natural sources and international transport); (3) the population exposed to concentrations in excess of the standard; (4) the presence and concentration of potentially toxic substances in the mix of particulate emissions in the area; and (5) the technological and economic feasibility of various control measures. In evaluating these factors, we have focused on the nature and extent of the nonattainment area problem and the technological and economic feasibility of additional control measures.

The South Coast Air Basin has made significant progress towards improving air quality and meeting the NAAQS despite challenges associated with being one of the nation's largest urban areas and meteorological conditions and mountainous terrain that tend to trap pollutants in the Air Basin.^[68] In the years prior to the adoption of the 2024 South Coast PM_2.5 Plan, CARB and the District developed and implemented several comprehensive plans ( e.g., the 2012 AQMP and 2016 AQMP) to provide for attainment of PM_2.5 and ozone NAAQS. These plans have resulted in the adoption and implementation of many new rules and amendments to existing rules across source categories. These regulations and strategies have yielded significant reductions from sources under the State's and District's jurisdictions. As a result of these already-adopted State and District measures, sources in the South Coast nonattainment area are already subject to the most stringent rules in the country, leaving fewer and more technologically challenging opportunities to reduce emissions, as demonstrated by the controls analysis in the 2024 South Coast PM_2.5 Plan.^[69] The State and District continue to pursue new opportunities to achieve further reductions in direct PM_2.5 and PM_2.5 precursor emissions, as outlined in the Plan; ^[70] however, the EPA acknowledges the scarcity of additional controls and the timeline needed to develop, adopt, and implement such measures. These factors generally support a longer time frame for attainment.

V. Summary of Proposed Action and Request for Public Comment

For the reasons discussed in this proposed rule, the EPA is proposing to grant the State's request for an extension of the Serious area attainment date from December 31, 2025, to December 31, 2030, based on a conclusion that the State has satisfied the requirements for such an extension in section 188(e) of the Act.

The EPA is soliciting public comments on the issues discussed in this document. We will accept comments from the public on this proposal for the next 30 days.

VI. Statutory and Executive Order Reviews

Additional information about these statutes and Executive Orders can be found at https://www.epa.gov/​laws-regulations/​laws-and-executive-orders.

A. Executive Order 12866: Regulatory Planning and Review and Executive Order 13563: Improving Regulation and Regulatory Review

This action is not a significant regulatory action and was therefore not submitted to the Office of Management and Budget (OMB) for review.

B. Executive Order 14192: Unleashing Prosperity Through Deregulation

This action is not expected to be an Executive Order 14192 regulatory action because this action is not significant under Executive Order 12866.

C. Paperwork Reduction Act (PRA)

This action does not impose an information collection burden under the PRA because this action does not impose additional requirements beyond those imposed by State law.

D. Regulatory Flexibility Act (RFA)

I certify that this action will not have a significant economic impact on a substantial number of small entities under the RFA. This action will not impose any requirements on small entities beyond those imposed by State law.

E. Unfunded Mandates Reform Act (UMRA)

This action does not contain any unfunded mandate as described in UMRA, 2 U.S.C. 1531-1538, and does not significantly or uniquely affect small governments. This action does not impose additional requirements beyond those imposed by State law. Accordingly, no additional costs to State, local, or Tribal governments, or to the private sector, will result from this action.

F. Executive Order 13132: Federalism

This action does not have federalism implications. It will not have substantial direct effects on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government.

G. Executive Order 13175: Coordination With Indian Tribal Governments

This action does not have Tribal implications, as specified in Executive Order 13175, because the SIP is not approved to apply on any Indian reservation land or in any other area where the EPA or an Indian Tribe has demonstrated that a Tribe has jurisdiction, and will not impose substantial direct costs on Tribal governments or preempt Tribal law. Thus, Executive Order 13175 does not apply to this action.

H. Executive Order 13045: Protection of Children From Environmental Health Risks and Safety Risks

The EPA interprets Executive Order 13045 as applying only to those regulatory actions that concern environmental health or safety risks that the EPA has reason to believe may disproportionately affect children, per the definition of “covered regulatory action” in section 2-202 of the Executive Order. Therefore, this action is not subject to Executive Order 13045 because it merely proposes to approve a state request for an attainment date extension as meeting Federal requirements. Furthermore, the EPA's Policy on Children's Health does not apply to this action.

I. Executive Order 13211: Actions That Significantly Affect Energy Supply, Distribution, or Use

This action is not subject to Executive Order 13211 because it is not a significant regulatory action under Executive Order 12866. ( printed page 35455)

J. National Technology Transfer and Advancement Act (NTTAA)

Section 12(d) of the NTTAA directs the EPA to use voluntary consensus standards in its regulatory activities unless to do so would be inconsistent with applicable law or otherwise impractical. The EPA believes that this action is not subject to the requirements of section 12(d) of the NTTAA because application of those requirements would be inconsistent with the CAA.

Authority: 42 U.S.C. 7401 et seq.

91 FR 35445